Pancratic lens

ABSTRACT

A positive, meniscus-shaped front lens unit has a convex front surface and a concave rear surface. The concave surface has a radius of curvature which is more than twice and less than ten times the radius of curvature of said convex surface. A single biconcave lens element is axially slidably mounted between said front lens unit and a positive rear main lens unit. The radius of curvature of the front surface of said biconcave lens element is more than twice and less than three times the radius of curvature of the rear surface of the bi-concave lens element. The biconcave lens element has an index of refraction nd3 and an Abbe number vd3 meeting the following conditions:

United Stati Muszumanski et a Feb. 6, 1973 1 1 PANCRATlC LENS [75]Inventors: Trude Muszumanski; lrmgard Wendiseh, both of Vienna, Austria[731 Assignees: Karl Vockenhuber and Ralmund Hauser, Vienna, Austria122] Filed: Sept. 8, 1970 [21] Appl. No.: 69,810

[30] Foreign Application Priority Data Sept. 26, 1969 Austria ..A9165/69 [52] US. Cl ..350/184, 350/214 [51] Int. Cl. ..G02b 15/14 [58]Field of Search ..350/l 84, 186

[56] References Cited UNITED STATES PATENTS 2,784,644 3/1957 Bednarz..350/184 3,348,898 10/1967 Baur et a1. ..350/l84 ll l s FOREIGN PATENTSOR APPLICATIONS 1,279,960 10/1968 Germany ..3SO/l84 PrimaryExaminer-John K. Corbin Artorney-Ernest G. Montague [57] ABSTRACT Apositive, meniscus-shaped front lens unit has a convex front surface anda concave rear surface. The concave surface has a radius of curvaturewhich is more than twice and less than ten times the radius of curvatureof said convex surface. A single biconcave lens element is axiallyslidably mounted between said front lens unit and a positive rear mainlens unit. The radius of curvature of the front surface of saidbiconcave lens element is more than twice and less than three times theradius of curvature of the rear surface of the biconcave lens element.The biconcave lens element has an index of refraction m and an Abbenumber v, meeting the following conditions:

It, s 1.63

llf! S 47 2 Claims, 5 Drawing Figures e v g g no u 12 PATENTED FEB 61975 SHEET 2 BF 2 FIG.4

PANCRATIC LENS This invention relates to a fast pancratic lens,particularly a projection lens, which comprises a positive,meniscus-shaped and, if desired, achromatic, front lens unit, which hasa convex front surface and concave rear surface having a radius ofcurvature which is more than twice and less then ten times the radius ofcurvature of the convex surface, a positive rear lens unit, and abiconcave lens unit, which is axially displaceable between said frontand rear lens units and has a rear surface and a front surface having aradius of curvature which is more than twice and less than three timesthe radius of curvature of the rear surface of said biconcave lens unit.A similar lens is known, e.g., from the German Utility ModelSpecification 1,814,231. The performance of such lenses is restricted toa zoom ratio (ratio of maximum to minimum focal length) of about 1.7 andan f-number of f/l.6. Whereas the Austrian Patent Specification 252,611discloses a lens of the kind defined first hereinbefore, it wasnecessary in said lens for the correction of chromatic aberrations tomake the front lens unit and the biconcave lens unit from cementedindividual lens elements. That requirement increased the expenditure andrequired lenses larger in diameter.

It is an object of the invention to avoid these disadvantages and topreserve the advantages as regards the zoom ratio and the relativeaperture. This is accomplished according to the invention in that thebiconcave lens unit and preferably also the meniscus are single lenselements and the index of refraction n and the Abbe number v of thebiconcave lens meet the following conditions:

V s B The invention will be now explained more fully hereinafter withreference to two embodiments shown by way of example on the drawing.

FIGS. 1 to 3 are axial sectional views showing a first projection lensin FIG. 1 as set to the smallest focal length and in FIG. 3 as set tothe largest focal length.

FIGS. 4 and 5 show a second projection lens also in its extremesettings.

With reference to the drawing, r,, r r,, .r are in millimeters the radiiof curvature of successive boundary surfaces of successive lenselements, d,, d,,,, (1,, d are in millimeters the center distancesbetween successive boundary surfaces, n '1 n m are the indices ofrefraction of successive lens elements, and v,,,, v,,,,,, v v are theAbbe numbers of successive lens elements.

The lens unit I is a positive meniscus lens having a convex frontsurface and consists preferably of a single lens element. As is apparentfrom the second embodiment shown in FIGS. 4 and 5, an achromatic frontlens unit I may also be employed. The relation between the two boundarysurfaces of the meniscus lens is defined by the condition Lens unit 11is a biconcave single lens element, whose surface having a larger radiusof curvature faces the lens unit I. It consists ofa glass for which andpositive lens element L For coma correction it is desirable to use lenselements L L and L having lower refractive indices than lens element L zn, li The center thickness d of lens element L should be related to thevertex distance d between said lens element L and the succeeding lenselement L by the inequation to 9 io whereas the center distance dbetween L1 and L and the center distance d between L and L are definedby the condition Technical data for the two embodiments shown by way ofexample are given hereinafter:

Relative aperture: f/ l .3 Zoom ratio: 2.02

d, 0.09/ n, 1.624 v, 47.0

d, 2.21 to 0.03

Relative aperture: f/l.3 Zoom ratio: 2.03

The data in the above tables are subject to the following tolerances:Radii of curvature of individual surfaces may differ to change therefractive power of the respective lens element by as much as 1'10percent. The thickness of each lens element may differ to change thefocal length of the respective lens element by as much as :0.03millimeter. The Abb numbers may differ up to :5.

What is claimed is:

l. A pancratic lens, comprising a positive, meniscus-shaped front lensunit having a convex front surface and a concave rear surface,

a positive rear lens unit, and

a single biconcave lens element axially slidably mounted between saidfront lens unit and said rear lens unit and having front and rearsurfaces,

said rear lens unit consists of positive first, second and third lenselements, a negative fourth lens element and a positive fifth lenselement, which succeed said biconcave lens element in that order,relative aperture: f/1.3

Zoom ratio: 2.02

d =0.34/ n 1.805/ v,,,.= 25.4 r,,=0.404

11., 0.18 n,,,=1.720/ v,,,,-- 50.4 r,,- 1.311

where r,, r r are in millimeters the radii of curvature of successiveboundary surface of successive lens elements, (1,, d d are inmilllmeters the center distances between successlve boundary surfaces, nn are the indices of refraction of successive lens elements, and v,,,, vv are the Abb numbers of successive lens elements.

2. A pancratic lens, comprising a positive, meniscus-shaped front lensunit having a convex front surface and a concave rear surface,

a positive rear lens unit, and

a single biconcave lens element axially slidably mounted between saidfront lens unit and said rear lens unit and having front and rearsurfaces,

said rear lens unit consists of positive first, second and third lenselements, a negative fourth lens element and a positive fifth lenselement, which succeed said biconcave lens element in that order,

Relative aperture: f/l .3

Zoom ratio: 2.03

where r,, r,,,, r,, r are in millimeters the radii of curvature ofsuccessive boundary surfaces of successive lens elements, d,, d d d arein millimeters the center distances between successive boundarysurfaces, 12, m 11, n are the indices of refraction of successive lenselements, and v, v v v are the Abbe numbers of successive lens elements.

* i k 0 l

1. A pancratic lens, comprising a positive, meniscus-shaped front lensunit having a convex front surface and a concave rear surface, apositive rear lens unit, and a single biconcave lens element axiallyslidably mounted between said front lens unit and said rear lens unitand having front and rear surfaces, said rear lens unit consists ofpositive first, second and third lens elements, a negative fourth lenselement and a positive fifth lens element, which succeed said biconcavelens element in that order, relative aperture: f/1.3 Zoom ratio: 2.02r1 + 3.561 d1 0.19 / nd1 1.504 / vd1 66.9 r2 + 54.555 d2 0.13 to 2.34r3 - 6.045 d3 0.09 / nd3 1.623 / vd3 56.9 r4 + 2.800 d4 2.24 to 0.03r5 + 6.505 d5 0.16 / nd5 1.589 / vd5 61.3 r6 - 44.288 d6 0.01 r7 + 1.708d7 0.19 / nd7 1.589 / vd7 61.3 r8 - 9.486 d8 0.04 r9 + 0.726 d9 0.31 /nd9 1.589 / vd9 61.3 r10 + 6.661 d10 0.12 r11 - 5.038 d11 0.34 / nd111.805 / vd11 25.4 r12 0.404 d12 0.22r13 0.704d13 0.18 / nd15 1.720 /vd13 50.4 r14 - 1.311 where r1, r2, . . . r14 are in millimeters theradii of curvature of successive boundary surface of successive lenselements, d1, d2, . . . d13 are in millimeters the center distancesbetween successive boundary surfaces, nd3, . . . nd13 are the indices ofrefraction of successive lens elements, and vd1, vd3, . . . vd13 are theAbbe numbers of successive lens elements.
 1. A pancratic lens,comprising a positive, meniscus-shaped front lens unit having a convexfront surface and a concave rear surface, a positive rear lens unit, anda single biconcave lens element axially slidably mounted between saidfront lens unit and said rear lens unit and having front and rearsurfaces, said rear lens unit consists of positive first, second andthird lens elements, a negative fourth lens element and a positive fifthlens element, which succeed said biconcave lens element in that order,relative aperture: f/1.3 Zoom ratio: 2.02 r1 + 3.561 d1 0.19 / nd1 1.504/ vd1 66.9 r2 + 54.555 d2 0.13 to 2.34 r3 - 6.045 d3 0.09 / nd3 1.623 /vd3 56.9 r4 + 2.800 d4 2.24 to 0.03 r5 + 6.505 d5 0.16 / nd5 1.589 / vd561.3 r6 - 44.288 d6 0.01 r7 + 1.708 d7 0.19 / nd7 1.589 / vd7 61.3 r8 -9.486 d8 0.04 r9 + 0.726 d9 0.31 / nd9 1.589 / vd9 61.3 r10 + 6.661 d100.12 r11 - 5.038 d11 0.34 / nd11 1.805 / vd11 25.4 r12 0.404 d12 0.22r130.704d13 0.18 / nd15 1.720 / vd13 50.4 r14 - 1.311 where r1, r2, . . .r14 are in millimeters the radii of curvature of successive boundarysurface of successive lens elements, d1, d2, . . . d13 are inmillimeters the center distances between successive boundary surfaces,nd3, . . . nd13 are the indices of refraction of successive lenselements, and vd1, vd3, . . . vd13 are the Abbe numbers of successivelens elements.